1. Field of the Invention
The present invention relates in general to the packaging and assembly of electronic circuitry and in particular to methods for mounting an imager to a support structure and circuitry and systems embodying the same.
2. Description of the Related Art
Charged-coupled device (CCD) imaging is a mature technology which has been used for many years for generating still or video images on any one of a number of display devices. While providing high quality images, CCD imagers have, at least until recently, been expensive. Since the cost of packaging the device was only a small fraction of the overall cost of the CCD imager, no significant efforts were made to trim packaging costs. However, as the cost of CCD imagers has dropped, the packaging costs have correspondingly become a significant factor in the overall cost of the packaged device. This cost factor is particularly relevant to consumer applications, such as digital cameras.
While CCD imagers produce high quality images, for lower cost-lower performance applications, again such as digital cameras, CMOS imagers are frequently used. While producing lower quality images, these imagers are relatively inexpensive, can be integrated onto a single chip along with ancillary circuitry, and allow for some active circuitry to be built within each pixel. In low-performance-low cost applications based on the less expensive CMOS technology, reducing package costs becomes more critical. Additionally, the use of the CMOS technology forces the makers of CCD imaging products to become more focused on reducing package costs.
One specific area where packaging is a significant factor relates to the packaging of the imager and its subsequent marriage to a printed circuit (PC) board or other support/interconnection structure. Presently, some CCD imagers are packaged in a conventional ceramic or plastic packages with a glass lid which allows photons to pass to the CCD element array. For small-format imagers, this type of packaging costs exceeds the cost of the imager chip itself. Moreover, this type of packaging is somewhat bulky and difficult to handle during PC board assembly. CCD imagers have also been packaged in QFP-style packages and in clear mold compound. These options are also not easy implement nor assemble to a PC board.
Thus, the need has arisen for methods of marrying CCD and CMOS imagers and similar photonic sensors to a support/interconnect structure such as a PC board. In addition, these methods should allow for the assembly of circuits and systems which are less expensive and more compact.